Ocean acidification has emerged as an extreme threat to marine ecosystems and fisheries – it may be the real threat from climate change, ready to blind-side us in just a few decades.
Why do I say that?
Our oceans have absorbed around one-third of the CO2 emitted so far. This (along with heat-absorption from the atmosphere) has had a moderating effect on temperature increases measured so far – climate change to date could have been worse than it is.
An unexpected problem has emerged, however.
When carbon dioxide dissolves in seawater it forms a weak acid (carbonic acid) – as CO2 has accumulated in oceans around the world, they have slowly but surely become more acidic (so far about one-tenth of one pH unit). Although the increase in acidity to date doesn’t seem like much, it is already having measurable biological and physical effects.
The main issue relates to the hardening (or calcification) of marine shells. Shell-forming organisms need a fairly narrow pH range to allow them to get calcium out of solution in seawater and deposit it in their shells.
But as the water becomes more acidic, shell calcification decreases, and at some point actually begins to reverse, causing shells and related structures (like coral reefs) to start dissolving – one study estimates that ALL coral reefs may cease to grow and start to dissolve when atmospheric CO2 reaches 560ppm. It is also likely that most regions will be inhospitable to coral reefs by 2050 (including Australia’s Great Barrier Reef).
This issue does not just affect oceans.
It affects all of us because it will cause major changes to marine food chains.
And if ocean ecosystems collapse, what happens to us?
Ocean acidification due to climate change
Further Reading
Acid In The Oceans: A Growing Threat To Sea Life
Can Corals Survive In A Warming World?
Report Warns about Carbon Dioxide Threats to Marine Life – download a PDF of “Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers.”
Ocean acidification: the other CO2 problem
